1. Field of the Invention
The present invention relates to a multiple function thin-film resistor-capacitor array, especially to a multiple function thin-film passive element having resistors with different resistances and capacitors of different capacitances formed on a single silicon substrate and used as optical substrate.
2. Description of Prior Art
The package for optical fiber receiving module or semiconductor device might incorporate passive elements such as resistor or capacitor for voltage regulation or noise filtering.
FIGS. 1 and 2 show package and capacitor element for a prior art optical fiber receiving module 1. As shown in FIG. 1, the optical fiber receiving module 1 comprises a base 11, a photodiode 12, an optical substrate 13, and a transimpedance amplifier (TIA) 14. According to required resistance and capacitance, a resistor 15 and two single layer capacitors (SLC) 16, 16′ are provided for voltage regulation or noise filtering. As to circuit connection for those elements, the photodiode 12 can be die bonded to the optical substrate 13 by silver epoxy and the position of the photodiode 12 can be adjusted by the thickness of the optical substrate 13. Afterward, the photodiode 12 is wire bonded and fixed to top face of the base 11 for TO-can architecture. Metal layers 162, 163 are added on surface of the dielectric layer 161 for the SLC 16 and 16′. The SLC can be integrated with the photodiode 12 by die bond and has electrical connection by wire bond. However, the capacitance value is affected by the thickness thereof. Therefore, the SLC cannot be used as optical substrate and the optical substrate 13 is additionally needed. The cost and processing time are increased.
FIGS. 3 to 5 show another prior art optical fiber receiving module 1. The optical fiber receiving module 1 comprises a base 11, a photodiode 12, an optical substrate 13, and a transimpedance amplifier (TIA) 14. According to required resistance and capacitance, an SMD resistor 17 and two SMD capacitors 18, 18′ are provided for voltage regulation or noise filtering. As to circuit connection for those elements, the photodiode 12 can be die bonded to the optical substrate 13. However, wire bond cannot be performed on the surface of the SMD resistor 17 and the SMD capacitors 18, 18′. Moreover, the two electrodes are coplanar. The SMD devices are die bonded on the substrate 19 and then the electrodes thereof are electrically connected, as shown in FIGS. 3 and 4. One of the SMD capacitors 18, 18′ can be arranged on the same optical substrate 13 with the photodiode 12 for circuit design and wire bonding. Afterward, those elements are electrically connected through wire bond, as shown in FIG. 5.
However, the prior art optical fiber receiving module 1 requires voltage regulator and filter unit composed of a plurality of resistors, capacitors, on an optical substrate. A plurality of die bond and wire bond processes are required for the photodiode 12. The cost is increased and the routing for the optical circuit and electrical circuit is limited. As the optical fiber receiving module becomes more compact, the device space is also limited because the SMD resistor and the SMD capacitor have their own standards. The position of the photodiode 12 is adjusted by the thickness of the optical substrate 13. The material cost is increase.